In elevator technology, several methods are used to produce the motive power for elevators. A common method is to use a traction sheave connected to a rotating motor hoisting the elevator car by means of ropes, with a counterweight placed on the opposite side of the traction sheave to balance the load. Another established solution is found in hydraulic elevators, in which the hoisting power to move the car is obtained from hydraulic cylinders either directly or via ropes. Most modern elevators are based on these solutions, of which many variations have been developed.
Although the above-mentioned elevator types have become established and are safe and reliable in operation, the solutions used in them comprise several factors that are objections of improvement and product development. For example, investigations are continuously being made to find ways of more effective utilisation of building space and reduction of energy consumption. For hydraulic elevators, the hoisting height is in practice limited to a few floors. By contrast, elevators with rope suspension have been installed in buildings as high as several hundred meters, in which case rope elongation and oscillation cause problems. Because of the rope suspension arrangements, the number of elevators in a shaft is practically limited to one.
In addition to rope-suspended and hydraulic elevators, several solutions for the use of a linear motor in an elevator have been proposed. In this case the electric motor is completely located in the shaft space. Most linear elevator motors have been based on the induction motor principle, although other motor types, such as a linear motor based on permanent magnets have also been presented. Several different solutions have been proposed, but as yet it has not been possible to produce a competitive elevator.